IT, Smart, Bradley, Brown, Horford are not overvalued. IT maybe by some. Even Crowder isn't. These guys are championship caliber pieces although none of them may be superstars there are stars there. There are also championship level top of the bench roleplayers there and quality championship level starters..
Guys like Zeller, KO, Green and Amir are basically about as average to below average placeholders and vets as they come. Honestly any big man of quality would be an upgrade to any of these guys. KO has the most value here.
Zizic, Yab and Young actually have nba level upside and could replace any of the above in the future.
Jackson, Mickey etc are about as average d-league fringe roster average prospects as they come. Jackson out of the two probably has more nba level upside. Rj Hunter was this too. Any of these guys could be cut without thinking twice minus maybe jackson. These guys are really no better than Gabe Pruitt.